feat(deacon): improve timing and add heartbeat command

Timing changes for more relaxed poke intervals:
- Daemon heartbeat: 60s → 5 minutes
- Backoff base: 60s → 5 minutes
- Backoff max: 10m → 30 minutes
- Fresh threshold: <2min → <5min
- Stale threshold: 2-5min → 5-15min
- Very stale threshold: >5min → >15min

New command:
- `gt deacon heartbeat [action]` - Touch heartbeat file easily

Template rewrite:
- Clearer wake/sleep model
- Documents wake sources (daemon poke, mail, timer callbacks)
- Simpler rounds with `gt deacon heartbeat` instead of bash echo
- Mentions plugins as optional maintenance tasks
- Explains timer callbacks pattern

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/daemon/types.go

@@ -34,7 +34,7 @@ type Config struct {
 func DefaultConfig(townRoot string) *Config {
 	daemonDir := filepath.Join(townRoot, "daemon")
 	return &Config{
-		HeartbeatInterval: 60 * time.Second,
+		HeartbeatInterval: 5 * time.Minute, // Deacon wakes on mail too, no need to poke often
 		TownRoot:          townRoot,
 		LogFile:           filepath.Join(daemonDir, "daemon.log"),
 		PidFile:           filepath.Join(daemonDir, "daemon.pid"),